Eugene Bartley wanted to know if his files would eventually disappear from a cloud-based backup service.

Cloud-based backup services, such as Mozy, Carbonite, and IDrive, upload your files to their servers as protection against your losing the originals. This has some big advantages over a local backup. Once set up they're completely automatic. And it's extremely unlikely that the same fire or flood will destroy your computer and your backup.

But there are disadvantages, as well. One is that you lose physical control of your backup. Those files could be destroyed because of someone else's corporate decision.

But that's not likely to happen--at least if you continue to pay your bill. But it's a good idea to know a service's policy.

Both Mozy and Carbonite will keep a file as long as it's on your drive (or at least the part of your drive that you're backing up), and for an additional 30 days after it disappears. That seems fair to me. If a file disappeared from your drive a month ago, and you haven't restored it, chances are you don't want it anymore.